1. Field of the Invention
The present invention relates to a dye image stabilization process for color photographic sensitive materials and particularly to a process for improving light fastness of dye images of color photographic sensitive materials.
2. Description of the Prior Art
In color photographic sensitive materials utilizing photosensitive silver halide, dye images are formed by the reaction of a color coupler with an oxidation product of a color developing agent, the reaction of a DDR coupler with an oxidation product of a color developing agent, oxidation of a dye developing agent, and bleaching dyes using development silver as a catalyst. However, the dyes or dye images (referred to as dye image, hereinafter) formed in such a manner fade or discolor due to the action of light like the case of dyes for conventional use, though the degree of fading or discoloration differs in each case.
Hitherto, various attempts have been made to prevent fading or discoloring of the above-described dye image caused by light (namely, to improve the light fastness of the dye image). However, a process having a sufficient effect has not been found.
For example, it has been known to use hydroquinone derivatives such as described in U.S. Pat. Nos. 2,360,290, 2,418,613, 2,675,314, 2,701,197, 2,704,713, 2,728,659, 2,732,300, 2,735,765, 2,710,801 and 2,816,028 and British Patent 1,363,921; gasslic acid derivatives such as described in U.S. Pat. Nos. 3,457,079 and 3,069,262 and Japanese Patent Publication No. 13496/68; p-alkoxyphenols such as described in U.S. Pat. Nos. 2,735,765 and 3,698,909; and chroman and coumaran derivatives such as described in U.S. Pat. Nos. 3,432,300, 3,573,050, 3,574,627, 3,764,337, 3,574,626, 3,698,909 and 4,015,990, etc., to prevent dye image fading. However, it cannot be said that these agents adequately prevent fading or discoloring of dye images.
Further, a process by which the stability of the dye images to light is improved using azomethine quenching compounds the absorption maximum of which is deeper than the absorption maximum of the dye forming the dye image has been described in British Pat. No. 1,451,000. However, this process is disadvantageous because the azomethine compound itself is intensely colored and the hue of the dye image is highly affected thereby.
In addition, a process has been known which comprises adding certain metal complexes to a color photographic sensitive material by which dye images formed thereafter are stabilized to light, as described in, for example, Japanese Patent Application (OPI) No. 87649/75 (the term "OPI" as used herein refers to a "published unexamined Japanese patent application") (U.S. Pat. No. 4,050,938) and Research Disclosure, 15162 (1976). However, metal complexes of this kind have problems in practical use as will be later discussed in Example 3 because:
(1) Not only do they not have so high an effect in preventing fading, but they also are difficult to add in adequate amounts to prevent fading because of their low solubility in the solvents commonly used for photographic additives.
(2) The hue and the purity of the dye images are adversely affected when the comples is added in a large amount, because the complex itself is intensely colored.
(3) Preparation of the photosensitive material is difficult, because the metal as a central atom of the complex has an unusually bad influence upon photographic properties.
(4) The fade preventing effect is reduced during processing steps such as development, etc., because the metal complex is subjected to modification.
U.S. Pat. No. 3,762,922 describes a process for improving light fastness which comprises carrying out development of a black-white photographic sensitive material containing a black coupler to couple it with an oxidation product of a color developing agent, and processing with a liquid containing heavy metal ions such as Cu, Co, Ni, Cd, Zn or Ag, etc., to form a chelate of the black dye formed by the above-described coupling. This process is different from the present invention in construction and effect, because the ligand forming the chelate with the metal ions is the dye itself and, consequently, the process can only be applied to black dye images.
In order to obviate these disadvantages of the prior art, the present inventors previously proposed a method for stabilizing organic substrate materials (e.g., dyes) to the action of light by making metal complexes having the following skeletal structure: ##STR1## wherein M represents Cu, Co, Ni, Pd or Pt; coexisting with the organic substrate materials (U.S. Patent Ser. No. 56,674, filed July 11, 1979) now U.S. Pat. No. 4,245,018. The metal complexes are excellent color fade preventing agents due to excellent solubility in an organic solvent and minimizing to worsen color hue or purity of color images.